IOtech Personal488, User Manual

Page: 120 / 150

Personal488 for Windows 95/98/Me/NT/2000
04-10-01
API Reference 6-52
SPoll
Syntax
INT WINAPI SPoll(DevHandleT devHandle);
DevHandle refers to either an interface or a specific external device.
Returns
-1 if error
otherwise, 0 or 64 (hardware interface) in the range 0 to 255 (external device)
Bus States
ATN
•
UNL, MLA, UNT, TAG, SPE, *ATN, ATN
•
SPD, UNT
Examples errorcode = SPoll(ieee); Returns the internal SRQ status
errorcode = SPoll(dmm);
Returns the Serial Poll response of the specified
device
See Also
SPollList, PPoll
In Active Controller mode, the
SPoll
(Serial Poll) command performs a Serial Poll of the bus device
specified and responds with a number from
0
to
255
representing the decimal equivalent of the eight-bit
device response. If
rsv
(
DIO7
, decimal value
64
) is set, then that device is signaling that it requires
service. The meanings of the other bits are device-specific.
Serial Polls are normally performed in response to assertion of the Service Request (
SRQ
) bus signal by
some bus device. In Active Controller mode, with the interface device specified, the
SPoll
command
returns the internal
SRQ
status. If the internal
SRQ
status is set, it usually indicates that the
SRQ
line is
asserted. Driver488 then returns a
64
. If it is not set, indicating that
SRQ
is not asserted, then Driver488
returns a
0
. With an external device specified,
SPoll
returns the Serial Poll status of the specified external
device.
In Peripheral mode, the
SPoll
command is issued only to the interface, and returns the Serial Poll status.
If
rsv
(
DIO7
, decimal value
64
) is set, then Driver488 has not been Serial Polled since the issuing last
Request
command. The
rsv
is reset whenever Driver488 is Serial Polled by the Controller.